Optical And Electrical Properties Of Porous Silicon And The Array Of Porous Silicon Of Preparation

Although silicon is the basic building block for most microelectronic fields, the material has not been used to provide optical transfer of information. The development of silicon-based optoelectronics has been severely limited, due to the small and indirect band gap of silicon in room temperature. The observation of visible luminescence from porous silicon by Canham in 1990 has begun to revitalize silicon's role as optical electronics materials, and the presentation of two-dimensional porous silicon photonic crystal extend this trend.In this paper, recent progress of porous silicon and its composites with organic materials were reviewed as well as the two-dimensional photonic crystal made from macro-porous silicon.μ-PCD, photoluminescence and FTIR were used to investigate the carrier recombination mechanism of porous silicon. It was shown that there was a correlation between PL and surface minor carrier lifetime, implying photoluminescence was the process of carrier recombination through surface state. The surface states on porous silicon will lower the minor carrier lifetime and enhance the photoluminescence. Aging and oxidation will passivate the surface of porous silicon and result in the lower PL peak and blueshift. It suggests that the surface states of porous silicon be responsible for the photoluminescence.A hybrid material was prepared by filling porous silicon with soluble conjugated polymer Poly (3-octylthiophene) (P3OT). A good heterojunction between n-type porous silicon and p-type P3OT was achieved. The hybrid material presented a strong photovoltaic (PV) effect, which was observed by means of surface photovoltaic spectroscopy (SPS). It was believed that the higher PV intensity was ascribed to the carrier transfer between the porous silicon and P3OT.The influence factors on the preparation of macroporous silicon arrays on patterned silicon wafer by electrochemical method were investigated. It was found that the pore diameter became larger and straighter with the increasing ofconcentration of HF. The lower current density led to fine surface of porous silicon. For the electrolyte, acetone made better control on the formation of porous silicon arrays than ethanol. Moreover, the anodic etching time also influenced the quality of pores. The longer of anodic etching time would lead to the pores with branches. By controlling the factors mentioned above, regular macropore arrays were obtained.